MG-5061A MARINE TRANSMISSION Caterpillar

General.

The MG 5061A is a reverse and reduction marine transmission, which offers helical gearing for quieter operation currently available in the following ratios : 1.13:1; 1.54:1; 1.75:1; 2.00:1 and 2.47:1.

This transmission is controlled completely by hydraulics. (See figure 2-5). Both the forward and the reverse clutches are operated by main pressure oil supply. The bearings, clutches, and gears are lubricated and cooled with low pressure oil.

Engine rotation (figure 2-1).

When shipped from the factory, each unit is designated for use with a particular engine rotation. Within their rated capacities, these units may be operated continuously in either forward or reverse. The unit can be adapted to either left-hand or right-hand engine rotation. To adapt to opposite engine rotation, remove the oil pump and gasket and replace them with the pump and gasket for the desired engine rotation. See the following chart for the pump to match the engine direction of rotation.

Direction of Drive.

The forward (input) clutch shaft and driving transfer gear (see figure 2-4) always rotate in engine direction. The reverse clutch shaft and driven transfer gear always rotate in anti-engine direction because the driven transfer gear is meshed with the driving transfer gear on the forward clutch shaft. When the forward clutch is engaged, the forward input pinion rotates in engine direction. The output gear, which is secured to the output shaft, is meshed with the forward input pinion and so the output gear and shaft are driven in anti-engine direction. When the reverse clutch is engaged, the reverse input pinion rotates in anti-engine direction. The output gear is meshed with the reverse input pinion and, therefore, the output gear and shaft are driven in engine direction.

Construction Features (See figures 2-3 and 2-4).

Housings.

The MG 5061A housing consists of an SAE 1, SAE 2 or SAE 3 adaptor and front and rear half housings. They are sealed together with an anaerobic plastic gasket coupound.

Taper roller bearings.

The forward, reverse and output shafts have taper roller bearings which require shimming to adjust endplay of the respective shafts.

Figure 2-1 : Marine Transmission Configurations for Right and Left-Hand Engines.

Oil pump drive.

The oil pump is tang connected and driven by the reverse clutch shaft.

Lubrication features.

Oil is directed by the control valve through horizontal drillings in the forward and reverse clutch shafts to orifices through which the front and rear roller bearings on the forward and reverse clutch shafts are lubricated. There are also orifices in the shafts through which both clutches are cooled.

Oil strainer.

The unit has an oil strainer mounted on the inlet side of the oil pump. The strainer is in the suction line between the sump and oil pump in the hydraulic circuit.

Specifications.

Table 1. provides general information relative to marine transmission operation. These specifications must be observed to obtain proper operation of the marine transmission.

Hose and Heat Exchanger Kit.

1. Heat Exchanger. The heat exchanger is designed to maintain the oil in the hydraulic system of the marine transmission at the proper temperature by passing coolant from the engine through the heat exchanger. Consequently, the heat exchanger should be installed in a location convenient to both engine coolant and marine transmission oil. Table 2 lists general data for heat exchanger requirements.

2. Heat exchangers furnished by Twin Disc to be used for salt water applications, have zinc rods installed at the inlet and outlet heads. See Figre 2-2). These rods must be checked every 90 days. If over 50 % of the rod is disintegrated, it should be replaced to provide effective protection.

3. Excessive corrosion of the zinc rod indicates electrolytic action. A careful inspection should be made to determine if this action is caused by a short circuit to external grounded electric current. These conditions must be eliminated to avoid the necessity of frequent replacement of the zinc rods. If these conditions do not exist, it is evident that the corrosion is due to local electrolysis. If rods are corroded with foreign material, they should be cleaned with a wire brush.

Figure 2-2 : Heat Exchanger (typical).

Figure 2-3 : Oil Pressure Check Points.

Figure 2-4 : MG 5061A Marine Transmission - Cross section.

Figure 2-5 : Hydraulic Schematic.